* {
    margin: 0;
    padding: 0;
}
.all {
    width: 100%;
    height: 100%;
    position: fixed;
    background-repeat: no-repeat;
    background-size: 100% 100%;
    background-image: url(../resource/壁纸.jpg);
}
.bg {
    width: 100%;
    height: 600px;
    display: flex;
    justify-content: center;
    align-items: center;
}
@mixin alert_one {
    width: 360px;
    height: 100px;
    margin-left: 20px;
}
.login_div {
    width: 400px;
    height: 400px;
    top: 200px;
    background-color: grey;
    border-radius: 5%;
    .title {
        @include alert_one;
        background-color:red;
    } 
    .center {
        @include alert_one;
        height: 200px;
        background-color: pink;
    }
    .bottom {
        @include alert_one;
        background-color: green;
    }
}

.title_font {
    width: 200px;
    height: 50px;
    // margin-top: 50px;
    margin-left: 100px;
}